Disallow references to extensions in classes

It's not clear in which order should the two receiver arguments be passed to
them, and there's no corresponding K*FunctionN class for now

 #KT-1183 In Progress

compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java

@@ -345,6 +345,10 @@ public interface Errors {
     DiagnosticFactory1<PsiElement, InferenceErrorData> TYPE_INFERENCE_UPPER_BOUND_VIOLATED = DiagnosticFactory1.create(ERROR);
     DiagnosticFactory2<PsiElement, JetType, JetType> TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH = DiagnosticFactory2.create(ERROR);
 
+    // Callable references
+
+    DiagnosticFactory1<JetExpression, CallableMemberDescriptor> EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED = DiagnosticFactory1.create(ERROR);
+
     // Multi-declarations
 
     DiagnosticFactory0<JetMultiDeclaration> INITIALIZER_REQUIRED_FOR_MULTIDECLARATION = DiagnosticFactory0.create(ERROR, DEFAULT);

compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/rendering/DefaultErrorMessages.java

@@ -440,6 +440,9 @@ public class DefaultErrorMessages {
 
         MAP.put(AMBIGUOUS_ANONYMOUS_TYPE_INFERRED, "Right-hand side has anonymous type. Please specify type explicitly", TO_STRING);
 
+        MAP.put(EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED,
+                "''{0}'' is a member and an extension at the same time. References to such elements are not allowed", TO_STRING);
+
         MAP.setImmutable();
 
         for (Field field : Errors.class.getFields()) {

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/BasicExpressionTypingVisitor.java

@@ -611,8 +611,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         ReceiverParameterDescriptor receiverParameter = descriptor.getReceiverParameter();
         ReceiverParameterDescriptor expectedThisObject = descriptor.getExpectedThisObject();
         if (receiverParameter != null && expectedThisObject != null) {
-            // TODO: report "extensions in classes" are not supported
-            context.trace.report(UNRESOLVED_REFERENCE.on(reference, reference));
+            context.trace.report(EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED.on(reference, descriptor));
             return null;
         }
 

compiler/testData/diagnostics/tests/callableReference/extensionInClassDisallowed.kt

@@ -0,0 +1,14 @@
+class A {
+    fun Int.extInt() = 42
+    fun A.extA(x: String) = x
+    
+    fun main() {
+        ::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>extInt<!>
+        ::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>extA<!>
+    }
+}
+
+fun main() {
+    A::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>extInt<!>
+    A::<!EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED!>extA<!>
+}

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -781,6 +781,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                 doTest("compiler/testData/diagnostics/tests/callableReference/extensionFromTopLevel.kt");
             }
             
+            @TestMetadata("extensionInClassDisallowed.kt")
+            public void testExtensionInClassDisallowed() throws Exception {
+                doTest("compiler/testData/diagnostics/tests/callableReference/extensionInClassDisallowed.kt");
+            }
+            
             @TestMetadata("genericClassFromTopLevel.kt")
             public void testGenericClassFromTopLevel() throws Exception {
                 doTest("compiler/testData/diagnostics/tests/callableReference/genericClassFromTopLevel.kt");